MOLECULAR GENETICS OF DIFFERENTIATION AND TRANSFORMATION

我们的主要关注点是识别和表征易位到 多发性骨髓瘤细胞系的IgH基因座(染色体14q32.3)和 肿瘤。核型14q32易位在20%-30%的 核型异常多发性骨髓瘤，但除11q13外 染色体很少被发现(因此命名为14Q+)。假设 免疫球蛋白易位将主要由异常的免疫球蛋白开关介导 重组，我们建立了一种全面的Southern印迹分析方法 识别重新排列的非法交换重组片段(ISRF) 其包含仅来自1个开关区的序列。已确定的18个ISRF中 并在MM细胞系中鉴定，通过克隆(9)确定了16个 在8个MM系中)或将另一个染色体易位到 高转换区。在21条MM线路的面板中，19条线路具有ISRF(15 或核型14q32易位(12个品系)。易位 在原发肿瘤中存在断点(确认为 产生了3个MM系，克隆自一个原发肿瘤，并在高 其他肿瘤的比例)。关于IGH，我们有四个结论 MM中的易位：1)它们几乎普遍存在，表明 多发性骨髓瘤核型分析的不可靠性；2)主要发生在 或接近IGH开关区域；3)它们涉及多样但非随机的(4p16 或约50%的肿瘤中的11q13)染色体配对阵列；以及4) Cyclin D1(11q13)和FGFR3(4p16.3)的调控失调分别发生在大约 25%的多发性骨髓瘤。一个次要的重点是确定一般性和 我们发现存在选择性表达的一种基因的意义 2个信息丰富的多发性骨髓瘤细胞系中的C-myc等位基因 涉及c-myc的易位、重排或扩增 轨迹。

Our major focus has been to identify and characterize translocations to the IgH locus (chromosome 14q32.3) in multiple myeloma (MM) cell lines and tumors. Karyotypic 14q32 translocations have been identified in 20-30% of karyotypically abnormal MM tumors, but apart from 11q13 the partner chromosome is rarely identified (thus designated 14q+). Hypothesizing that IgH translocations will be mediated mainly by aberrant IgH switch recombination, we developed a comprehensive Southern blot assay to identify rearranged illegitimate switch recombination fragments (ISRF) that contain sequences from only 1 switch region. Of 18 ISRFs identified and characterized in MM cell lines, 16 have been determined by cloning (9 in 8 MM lines) or mapping to be translocations of another chromosome to an IgH switch region. In a panel of 21 MM lines, 19 have either an ISRF (15 lines) or a karyotypic 14q32 translocations (12 lines). The translocation breakpoints are present in primary tumors (confirmed for tumors that generated 3 MM lines, cloned from one primary tumor, and ISRFs in a high proportion of other tumors). We have 4 conclusions regarding IgH translocations in MM: 1) they occur almost universally, indicating the unreliability of karyotypic analysis in MM; 2) they occur principally into or near IgH switch regions; 3) they involve a diverse but non-random (4p16 or 11q13 in about 50% of tumors) array of chromosomal partners; and 4) dysregulation of cyclin D1 (11q13) and FGFR3 (4p16.3) each occur in about 25% of MM tumors. A minor focus is to determine the generality and significance of our finding that there is selective expression of one c-myc allele in 2 informative MM cell lines despite the apparent absence of translocation, rearrangement, or amplification involving the c-myc locus.